1. Field of the Invention
The present invention relates to a semiconductor laser structure and, more particularly, to a high-output semiconductor laser demanded for reproduction.
2. Description of the Prior Art
A single-mode semiconductor laser which is free from astigmatism and has a lasing wavelength ranging from 780 to 830 nm is demanded for use as a light source for writing and reading data onto and from an optical disk. The self-aligned structure semiconductor laser is one of the most promising laser devices which can satisfy the above-described requirements. One type of conventional self-aligned structure semiconductor laser has been reported by S. Nakatsuka et al. (see Extended Abstracts of the 15th Conference on Solid State Device and Materials (1983) p. 297 to 300).
FIG. 2 shows the structure of a self-aligned structure semiconductor laser according to this prior art. In the production of a semiconductor laser having this structure, when a channel stripe is formed, the p-GaAlAs cladding layer 4 which defines the bottom of the channel is exposed to the atmosphere. Since the P-GaAlAs cladding layer 4 is oxidized considerably easily, at the same time as it is exposed to the atmosphere, the exposed surface 10 is oxidized. The oxide thus formed is undesirably left at the regrowth interface even after a crystal has been regrown on the exposed surface 10 of the p-GaAlAs cladding layer 4 and on the n-type GaAs blocking layer 5. Moreover, this oxide is present on the current path.
Thus, the above-described prior art suffers from the following problems. Namely, due to the oxide remaining at the regrowth interface, the electrical characteristics of the resultant laser device are considerably inferior, i.e., the threshold voltage of the current-voltage character of the device is 1.9 V, and the series resistance 5.OMEGA.. Accordingly, the yield of the device is undesirably low. In addition, the presence of the oxide at the regrowth interface causes the life of the device to be extremely shortened and prevents the device from being reliable.